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Abstract

We determine group index and group velocity dispersion (GVD) of SOI single-mode strip waveguides (photonic wires) with 525×226nm cross-section over the entire telecommunication bandwidth by employing an integrated Mach-Zehnder interferometer. The measured GVD yields 4400 ps/(nm∙km) at 1550 nm and exceeds that of standard single-mode fibers by almost three orders of magnitude. In the photonic wires the GVD is mainly determined by strong light confinement rather than by material dispersion. Our results indicate that despite this high GVD, dispersion-induced signal impairment is negligible in photonic circuits for data rates up to 100-Gb/s and total waveguide lengths as long as about 1 meter. The measured group index and GVD are used as benchmarks to compare model calculations originating from four different theoretical methods.

Figures (5)

Phase-space for the two lowest order TE and TM modes as a function of the waveguide width for three Si slab thicknesses h: (a) 300nm, (b) 226nm and (c) 150nm. The cutoff wavelengths (black lines) are determined by band structure calculations. The grey areas show single-mode support for both TE and TM polarization, grey hatched areas showing truly TE support. Red circles and blue squares correspond to experimentally measured TE- and TM cutoffs, respectively.

Group indices derived from transmission spectra in TE and TM polarization and compared with model calculations based on plane-wave (dotted), beam-propagation (dashed), eigenmode expansion (solid), and FDTD (dash-dot). Red and blue dots correspond to measurements applying either laser diodes or a broadband LED light source, respectively. Inset: Spectral range of the TE group index used for further evaluation of the dispersion parameter.